Study helps calm extinction fears

Scientists say more taxonomists and lower estimate of numbers mean most species may be named this century.

Researchers say the number of existing species, including the striped sea slug (above), is between 3 million and 5 million, of which 1.5 million have been named. Photo / Supplied

A New Zealand researcher has challenged long-held claims that most species will be wiped out before they can even be discovered.

In what is being called good news for global biodiversity conservation efforts, a study by researchers from the University of Auckland, Griffith University and the University of Oxford, published today in the journal Science, argues the bleak claims had been based on misconceptions.

They say the number of existing species has been over-estimated and is instead likely to total between about 3 million and 5 million, of which around 1.5 million have been named.

The researchers also disagree with claims that the number of taxonomists, who describe and identify species, is in decline.

Rather, they conclude there have never been so many people - professionals and amateurs alike - describing new species.

The number of taxonomists may now be 50,000 and growing, in large part due to the development of science in Asia and South America, regions that are rich in biodiversity and where many new species are being discovered.

"Over-estimates of the number of species on Earth are self-defeating because they can make attempts to discover and conserve biodiversity appear to be hopeless," said Associate Professor Mark Costello from the University of Auckland.

"Our work suggests that this is far from the case. We believe that with just a modest increase in effort in taxonomy and conservation, most species could be discovered and protected from extinction."

Having compiled a global database of named marine species, the researchers were left astonished to see that a graph of the rate of discovery of new species was a straight line, with seemingly no end in sight.

On closer inspection, they were more surprised to find that this was being maintained by an increasing number of taxonomists.

"This suggests that without greater effort the rate of discovery would be levelling off - that is, we have discovered at least half of all species on Earth," Dr Costello said.

"Many papers and websites say that the number of taxonomists has been decreasing but without providing data - but our database actually had the names of every scientist who named a species."

With this increasing effort, significantly due to an increase in expertise in Asia and South America, along with a less unattainable estimate of the number of species on Earth, the researchers believe most species will be named this century.

But they do not underplay risks to species and their habitats, threatened by over-hunting, habitat loss and climate change now occurring at both local and global scales.

The discovery and naming of species, giving its existence formal recognition, was critical to their conservation.

The process of discovery, including exploration of remote and less studied habitats, also provided the evidence to underpin conservation efforts.

This was especially crucial in New Zealand, which boasts more endemic marine species than any country in the world.

"Not only is there a high richness of species in New Zealand, but they do not occur anywhere else," Dr Costello said.

"This means we have a special need to have national taxonomic expertise both to know our native species, and identify any introduced species that may become pests."